U.S. patent application number 13/761638 was filed with the patent office on 2013-08-08 for piezoelectric element, liquid ejecting head and liquid ejecting apparatus.
This patent application is currently assigned to SEIKO EPSON CORPORATION. The applicant listed for this patent is SEIKO EPSON CORPORATION. Invention is credited to Eiju HIRAI.
Application Number | 20130201258 13/761638 |
Document ID | / |
Family ID | 48902526 |
Filed Date | 2013-08-08 |
United States Patent
Application |
20130201258 |
Kind Code |
A1 |
HIRAI; Eiju |
August 8, 2013 |
PIEZOELECTRIC ELEMENT, LIQUID EJECTING HEAD AND LIQUID EJECTING
APPARATUS
Abstract
A configuration is provided in which at least one end of a
piezoelectric body active portion is defined by an end of a second
electrode, a portion of configuring the piezoelectric body active
portion of a first electrode is covered with a piezoelectric body
layer, the first electrode and the piezoelectric body layer are
extended to the outside of the end of the second electrode which
defines the end of the piezoelectric body active portion, the first
electrode includes an exposure portion which is not covered with
the piezoelectric body layer and extends further outside than the
end of the second electrode, and on the end of the piezoelectric
body layer which forms the exposure portion, an independent
electrode which is electrically independent from the second
electrode is provided.
Inventors: |
HIRAI; Eiju; (Okaya,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEIKO EPSON CORPORATION; |
Tokyo |
|
JP |
|
|
Assignee: |
SEIKO EPSON CORPORATION
Tokyo
JP
|
Family ID: |
48902526 |
Appl. No.: |
13/761638 |
Filed: |
February 7, 2013 |
Current U.S.
Class: |
347/70 ;
310/365 |
Current CPC
Class: |
H01L 41/047 20130101;
H01L 41/29 20130101; B41J 2/14233 20130101; B41J 2002/14419
20130101; B41J 2002/14491 20130101; H01L 41/0973 20130101; H01L
41/0471 20130101; B41J 2002/14241 20130101 |
Class at
Publication: |
347/70 ;
310/365 |
International
Class: |
H01L 41/047 20060101
H01L041/047; B41J 2/14 20060101 B41J002/14 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 8, 2012 |
JP |
2012-024885 |
Claims
1. A piezoelectric element comprising: a first electrode provided
on a vibration plate; a piezoelectric body layer provided on the
first electrode; and a second electrode provided on the
piezoelectric body layer, wherein at least one end of a
piezoelectric body active portion in which the piezoelectric body
layer is interposed between the first electrode and the second
electrode is defined by an end of the second electrode, wherein the
first electrode has a portion configuring the piezoelectric body
active portion covered with the piezoelectric body layer, and the
first electrode and the piezoelectric body layer are extended to
the outside of the end of the second electrode which defines the
end of the piezoelectric body active portion, wherein the first
electrode includes an exposure portion which is not covered with
the piezoelectric body layer and extends to further outside than
the end of the second electrode, and wherein on the end of the
piezoelectric body layer which forms the exposure portion, an
independent electrode which is electrically independent from the
second electrode is provided.
2. The piezoelectric element according to claim 1, wherein a
through hole configuring the exposure portion is formed on the
piezoelectric body layer which is present further outside than the
end of the second electrode, and wherein the independent electrode
is continuously provided over the periphery of the through
hole.
3. The piezoelectric element according to claim 1, wherein the
independent electrode is formed of the same material as that of the
second electrode.
4. A liquid ejecting head comprising: a plurality of pressure
generation chambers communicating with nozzles ejecting a liquid;
and the piezoelectric element according to claim 1, which causes a
pressure change in each pressure generation chamber.
5. A liquid ejecting head comprising: a plurality of pressure
generation chambers communicating with nozzles ejecting a liquid;
and the piezoelectric element according to claim 2, which causes a
pressure change in each pressure generation chamber.
6. A liquid ejecting head comprising: a plurality of pressure
generation chambers communicating with nozzles for ejecting liquid;
and the piezoelectric element according to claim 3, which causes a
pressure change in each pressure generation chamber.
7. The liquid ejecting head according to claim 4, wherein the first
electrodes configuring each piezoelectric element are formed in a
strip shape, and are respectively connected to each other via a
connection wire which is connected to the exposure portion so as to
configure a common electrode which is common to a plurality of the
piezoelectric elements.
8. A liquid ejecting apparatus comprising: the liquid ejecting head
according to claim 4.
9. A liquid ejecting apparatus comprising: the liquid ejecting head
according to claim 5.
10. A liquid ejecting apparatus comprising: the liquid ejecting
head according to claim 6.
11. A liquid ejecting apparatus comprising: the liquid ejecting
head according to claim 7.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present invention relates to a piezoelectric element
having a first electrode, a piezoelectric body layer and a second
electrode, and a liquid ejecting head and a liquid ejecting
apparatus which include the piezoelectric element.
[0003] 2. Related Art
[0004] A typical example of a liquid ejecting head mounted on a
liquid ejecting apparatus includes an ink jet type recording head
which ejects ink droplets from a nozzle. Although configurations of
the ink jet type recording head are diversified, for example, there
is a configuration in which the ink droplets are ejected by a
piezoelectric element being driven. The piezoelectric element is
provided on a vibration plate configuring one surface of a pressure
generation chamber. The vibration plate is deformed by the driven
piezoelectric element. Thereby, the pressure in the pressure
generation chamber is increased and thus the ink droplets are
ejected from the nozzle communicating with the pressure generation
chamber.
[0005] Further, the piezoelectric element mounted on the liquid
ejecting head or the like includes, for example, a deflecting
vibration mode of the piezoelectric element configured such that a
piezoelectric body layer formed of a piezoelectric material that
exhibits an electrical-mechanical conversion function is interposed
between a first electrode and a second electrode.
[0006] In the above configuration of the piezoelectric element, for
example, due to moisture or the like, a leakage current occurs
between the first electrode and the second electrode, and thereby
there is a possibility that the piezoelectric body layer may be
destroyed. In order to suppress such destruction of the
piezoelectric body layer, for example, there is a piezoelectric
element which is covered with a protection film. Further, for
example, a surface of the piezoelectric body layer is covered with
an upper electrode (second electrode), so that the occurrence of
the leakage current between a lower electrode (first electrode) and
the upper electrode (second electrode) is suppressed (refer to
JP-A-2009-172878).
[0007] As is in the invention according to JPA-2009-172878, by
covering the surface of the piezoelectric body layer with the
second electrode, it is possible to suppress the destruction of the
piezoelectric body layer. However, as shown in FIG. 4 of
JP-A-2009-172878, there may be a case where an exposure portion of
the piezoelectric body layer needs to be separately covered with a
protection film. That is, there is a possibility that the
destruction of the piezoelectric body layer may not be sufficiently
suppressed without the protection film.
[0008] Such a problem is present not only in the ink jet type
recording head, but also in other liquid jet heads ejecting a
liquid other than the ink.
SUMMARY
[0009] An advantage of some aspects of the invention is that it
provides a piezoelectric element, a liquid ejecting head and a
liquid ejecting apparatus which are able to sufficiently suppress
destruction of a piezoelectric body layer.
[0010] According to an aspect of the invention, there is provided a
piezoelectric element including: a first electrode provided on a
vibration plate; a piezoelectric body layer provided on the first
electrode; and a second electrode provided on the piezoelectric
body layer, wherein at least one end of the piezoelectric body
active portion in which the piezoelectric body layer is interposed
between the first electrode and the second electrode, is defined by
an end of the second electrode, wherein the first electrode has a
portion configuring of the piezoelectric body active portion
covered with the piezoelectric body layer, and the first electrode
and the piezoelectric body layer are extended to the outside of the
end of the second electrode which defines the end of the
piezoelectric body active portion, wherein the first electrode
includes an exposed portion which is not covered with the
piezoelectric body layer and extends further outside than the end
of the second electrode, and wherein an independent electrode which
is electrically independent from the second electrode is provided
on the end of the piezoelectric body layer which forms the exposure
portion.
[0011] In the aspect of the invention, it is possible to
effectively suppress occurrence of a leakage current between the
first electrode and the second electrode, and to sufficiently
suppress the destruction of the piezoelectric body layer resulting
from the leakage current without covering the piezoelectric body
layer with the protection film. Further, by providing the
independent electrode, the disconnection due to over-etching the
first electrode, which occurs when patterning the second electrode,
can be suppressed.
[0012] Here, for example, in a case where a through hole
configuring the exposure portion is formed on the piezoelectric
body layer which is present further outside than the end of the
second electrode, it is preferable that the independent electrode
be continuously provided over the periphery of the through hole. As
a result, the leakage current between the first electrode and the
second electrode can be more reliably suppressed from
occurring.
[0013] Further, it is preferable that the independent electrode be
formed of the same material as the second electrode. As a result,
the independent electrode can be simultaneously formed when forming
the second electrode and thus the manufacturing cost can be
reduced.
[0014] Further, according to another aspect of the invention, there
is provided a liquid ejecting head including a plurality of
pressure generation chambers communicating with nozzles ejecting a
liquid, and the piezoelectric element, as described above, which
causes a pressure change in each pressure generation chamber.
[0015] In the aspect of the invention, a liquid ejecting head
capable of enhancing the durability and reliability of the
piezoelectric element can be realized.
[0016] Here, it is preferable that the first electrodes configuring
the piezoelectric element be formed in a strip shape, and be
respectively connected to each other via a connection wire which is
connected to the exposure portion so as to configure a common
electrode which is common to a plurality of the piezoelectric
elements. As a result, since the exposure portion of the first
electrode is covered with the connection wire, the destruction of
the piezoelectric layer due to the leakage current can be more
reliably suppressed from occurring.
[0017] Furthermore, according to still another aspect of the
invention, there is provided a liquid ejecting apparatus including
the liquid ejecting head described above. In the aspect of the
invention, a liquid ejecting apparatus having improved durability
and reliability of the piezoelectric element can be realized.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The invention will be described with reference to the
accompanying drawings, wherein like numbers reference like
elements.
[0019] FIG. 1 is an exploded perspective view of a recording head
according to an embodiment of the present invention.
[0020] FIG. 2A is a plan view and FIG. 2B is a cross-sectional view
of the recording head according to an embodiment of the present
invention.
[0021] FIG. 3 is a plan view illustrating a structure of a
piezoelectric element according to an embodiment of the present
invention.
[0022] FIGS. 4A and 4B are cross-sectional views illustrating a
structure of a piezoelectric element according to an embodiment of
the present invention.
[0023] FIGS. 5A to 5D are cross-sectional views illustrating a
method of manufacturing a recording head according to an embodiment
of the present invention.
[0024] FIGS. 6A to 6C are cross-sectional views illustrating a
method of manufacturing a recording head according to an embodiment
of the present invention.
[0025] FIGS. 7A and 7B are plan views illustrating a method of
manufacturing a recording head according to an embodiment of the
present invention.
[0026] FIG. 8A is a plan view and FIG. 8B is a cross-sectional view
illustrating a modification example of a recording head according
to an embodiment of the present invention.
[0027] FIG. 9A is a plan view and FIG. 9B is a cross-sectional view
illustrating a modification example of a recording head according
to an embodiment of the present invention.
[0028] FIG. 10 is a schematic diagram of a recording apparatus
according to an embodiment of the present invention.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0029] Hereinafter, the invention will be described in detail with
reference to an exemplary embodiment of the present invention.
[0030] FIG. 1 is an exploded perspective view of an ink jet
recording head which is an example of a liquid ejecting head
according to an embodiment of the present invention, and FIG. 2A is
a plan view of FIG. 1, and FIG. 2B is a cross-sectional view taken
along line IIB-IIB in FIG. 2A.
[0031] As shown in the drawing, in a flow path forming substrate
10, pressure generation chambers 12 are provided side by side,
which are partitioned by a plurality of partition walls 11 in the
width direction (the lateral direction). Further, in one end side
in the longitudinal direction of the pressure generation chamber 12
of the flow path forming substrate 10, an ink supply path 13 and a
communication path 14 are partitioned by the partition wall 11. In
addition, in one end of the communication path 14, a communication
section 15 configuring a portion of a manifold 100 which is a
common ink chamber (liquid chamber) of each pressure generation
chamber 12 is formed. That is, in the flow path forming substrate
10, a liquid flow path formed of the pressure generation chamber
12, the ink supply path 13, the communication path 14 and the
communication section 15 are provided.
[0032] On one side surface of the flow path forming substrate 10, a
vibration plate 50 is formed. The vibration plate 50 according to
the present embodiment is configured by an elastic film 51 formed
on the flow path forming substrate 10 and an insulator film 52
formed on the elastic film 51. In addition, on the other side
surface of the flow path forming substrate 10, a nozzle plate 20
where a nozzle 21 communicating with each pressure generation
chamber 12 is protruded is bonded. Further, a liquid flow path of
the pressure generation chamber 12 is formed by anisotropically
etching the flow path forming substrate 10 from the other side
surface and the one side surface of the liquid flow path of the
pressure generation chamber 12 is configured of the vibration plate
50 (elastic film 51).
[0033] On the insulator film 52 configuring the vibration plate 50,
a piezoelectric element 300 configured by a first electrode 60, a
piezoelectric body layer 70 and a second electrode 80 is formed. In
the piezoelectric body layer configuring the piezoelectric element
300, a voltage distortion occurs by applying a voltage to both
electrodes at a portion interposed between the first electrode 60
and the second electrode 80. A substantial drive portion where the
voltage distortion of the piezoelectric element 300 occurs is
referred to as a piezoelectric body active portion 320.
[0034] In addition, with the first electrode 60 and the second
electrode 80 configuring the piezoelectric element 300, any one
electrode configures a common electrode that is common to a
plurality of the piezoelectric elements 300 and the other electrode
is patterned for each pressure generation chamber 12 and then
configures an individual electrode which is independent for each
piezoelectric element 300. In the present embodiment, it is assumed
that the first electrode 60 is the common electrode which is common
to the plurality of piezoelectric elements 300, and the second
electrode 80 is the individual electrode which is independent for
each piezoelectric element 300.
[0035] Further, the configuration of the piezoelectric element 300
of the present embodiment will be described in detail with
reference to FIGS. 3, 4A and 4B. In addition, FIG. 3 is a plan view
illustrating a configuration of the piezoelectric element and FIG.
4A is a sectional view taken along line IVA-IVA and FIG. 4B is a
sectional view taken along line IVB-IVB of FIG. 3.
[0036] As illustrated in FIGS. 3, 4A and 4B, the first electrode 60
is independently provided for each piezoelectric element 300,
opposing each pressure generation chamber 12. The first electrode
60, for example, is formed in a strip shape on the insulator film
52 configuring the vibration plate 50, opposing to each pressure
generation chamber 12. In addition, the first electrode 60 is
formed with a narrower width than the width of the pressure
generation chamber 12, and in the longitudinal direction (the
longitudinal direction of the pressure generation chamber 12) of
the piezoelectric element 300, both ends are provided so as to be
located outside of the pressure generation chamber 12,
respectively. Although details thereof will be described later, the
respective first electrodes 60 which are provided in the strip
shape are connected to each other by a connection wire outside of
the pressure generation chamber 12 and configure a common electrode
that is common to the plurality of piezoelectric elements 300.
[0037] The piezoelectric body layer 70, being independent in a
portion opposing each pressure generation chamber 12, is provided
continuously along the parallel arrangement direction of the
pressure generation chamber 12 in the area outside the pressure
generation chamber 12 in the longitudinal direction. That is, the
piezoelectric body layer 70 is provided continuously in the portion
corresponding to the plurality of pressure generation chambers 12
which are arranged in parallel, with the exception of a through
groove 71 formed in the portion opposing the partition wall 11
which partitions each pressure generation chamber 12.
[0038] The portion opposing the pressure generation chamber 12 of
the piezoelectric body layers 70 is formed with a wider width than
the width of the first electrode 60 and with a narrower width than
the width of the pressure generation chamber 12. In the
longitudinal direction (the longitudinal direction of the pressure
generation chamber 12) of the piezoelectric element 300, the
piezoelectric body layer 70 is formed continuously to the outside
of the pressure generation chamber 12. More specifically, both ends
of the piezoelectric body layer 70 are located further outside than
the end of the first electrode 60. The first electrode 60 is
covered with the piezoelectric layer 70.
[0039] As the material of the piezoelectric body layer 70, for
example, a ferroelectric piezoelectric material such as zirconate
titanate lead (PZT), a relax ferroelectric body in which metal such
as niobium, nickel, magnesium, bismuth or yttrium is added thereto,
a lead-free piezoelectric material that does not contain lead such
as bismuth titanate are used.
[0040] The second electrode 80 is isolated for each pressure
generation chamber 12 and configures the individual electrode of
each piezoelectric element 300. A portion opposing each pressure
generation chambers 12 of the second electrode 80 is formed with
substantially the same width as that of the piezoelectric layer 70.
In addition, in the longitudinal direction of the piezoelectric
element 300, the second electrode 80 is also extended to the
outside of the pressure generation chamber 12.
[0041] In other words, the piezoelectric body active portion 320
which is a substantial drive portion of the piezoelectric element
300 is provided so as to oppose each pressure generation chamber
12, and both ends of the piezoelectric body active portion 320 in
the longitudinal direction of the piezoelectric element 300 are
located outside the pressure generation chamber 12.
[0042] Here, at least one end of the piezoelectric body active
portion 320 in the longitudinal direction of the piezoelectric
element 300 is defined by an end of the second electrode 80. For
example, in the present embodiment, in the ink supply path 13 side
of the pressure generation chambers 12, an end of the piezoelectric
body active portion 320 is defined by an end of the second
electrode 80.
[0043] That is, in the ink supply path 13 side of the pressure
generation chamber 12, the end of the second electrode 80 is
located further inside (the pressure generation chamber 12 side)
than the end of the first electrode 60. In other words, in the ink
supply path 13 side of the pressure generation chamber 12, the
first electrode 60 and the piezoelectric body layer 70 are extended
to the outside of the end of the second electrode 80.
[0044] On the piezoelectric layer 70 that is extended to the
outside of the end of the second electrode 80, for example, a
connection wire 90 made of gold (Au) or the like is provided. The
connection wire 90 is connected to the first electrode 60 which is
provided corresponding to each pressure generation chamber 12 in a
strip shape and configures a portion of the common electrode of the
piezoelectric element 300. In addition, a portion of the common
electrode is configured by the connection wire 90 and thereby it is
possible to decrease resistance of the common electrode.
[0045] The first electrode 60 as described above is basically
covered with the piezoelectric body layer 70. However, an exposure
portion 61 which exposes a surface which is not covered with the
piezoelectric body layer 70 is provided on the outside further than
the end of the second electrode 80. In the present embodiment, a
through hole 72 configuring the exposure portion 61 on the
piezoelectric body layer 70 that is extended to the outside of the
second electrode 80 is formed. Then, the connection wire 90 is
connected to each first electrode 60 through the through hole
72.
[0046] Here, at a peripheral portion of the through hole 72 of the
piezoelectric body layer 70, which configures the exposure portion
61, that is, at the end of the piezoelectric layer 70 forming the
exposure portion 61, an independent electrode 85 which is
independent from the second electrode 80 is formed. The independent
electrode 85 is continuously formed over the periphery of the
through hole 72.
[0047] By such an independent electrode 85 being provided, it is
possible to suppress the occurrence of the leakage current between
the first electrode 60 and the second electrode 80, and accordingly
it is possible to effectively suppress the destruction of the
piezoelectric body layer 70 resulting from the leakage current. For
example, even if the piezoelectric layer 70 is not covered with the
protection film or the like, it is possible to suppress the
destruction of the piezoelectric body layer 70. In addition, the
independent electrode 85 is provided in a form of a separate island
which is independent from the first electrode 60 and the second
electrode 80. Therefore, the leakage does not occur between the
independent electrode 85 and the first electrode 60 or between the
independent electrode 85 and the second electrode 80.
[0048] Materials of the independent electrode 85 are not
particularly limited. However, it is preferable to be formed with
the same material as that of the second electrode 80. Since the
independent electrode 85 can be formed simultaneously with the
second electrode 80, the manufacturing cost can be suppressed from
increasing.
[0049] Incidentally, the second electrode 80 is extended to the end
of the piezoelectric body layer 70 at the opposite side to the ink
supply path 13 of the pressure generation chamber 12. That is, the
end of the second electrode 80 is located further outside than the
end of the first electrode 60, and the end of the piezoelectric
body active portion 320 is defined by the end of the first
electrode 60. Then the second electrode 80 has a wide portion 81
which is wider than the width of the pressure generation chamber 12
at both sides of the pressure generation chamber 12 (refer to FIG.
2A). Accordingly, the vibration plate 50 opposing the pressure
generation chamber 12 is formed with a substantially uniform
thickness and thus there is no partially thinned portion.
Therefore, it is possible to suppress the occurrence of cracks or
the like on the vibration plate 50 when driving the piezoelectric
element 300.
[0050] On the flow path forming substrate 10 where such a
piezoelectric element 300 is formed, the protection substrate 30 is
adhered by an adhesive 35. On the protection substrate 30, a
manifold section 31 which configures at least a portion of a
manifold 100 is provided. The manifold section 31 passes through
the protection substrate 30 in the thickness direction, and is
formed over the width direction of the pressure generation chamber
12, and thus communicates with the communication section 15 of the
flow path forming substrate 10, as described above, so as to
configure the manifold 100.
[0051] Further, in a region opposing the piezoelectric element 300
of the protection substrate 30, a piezoelectric element holding
section 32 is provided. The piezoelectric element holding section
32 may have a space of such an extent that does not disturb the
movement of the piezoelectric element 300 and the space may be
sealed or may not be sealed.
[0052] As such a protection plate 30, it is preferable to use the
material having substantially the same thermal expansion
coefficient as the flow path forming substrate 10, for example,
glass, ceramic material or the like. In the present embodiment, as
the material of the protection substrate 30, the silicon single
crystal substrate of the same material as the flow path forming
substrate 10 is used.
[0053] On the protection substrate 30, a compliance substrate 40
formed of a sealing film 41 and a fixing plate 42 is bonded. The
sealing film 41 is made of a material having flexibility and a low
rigidity. One surface of the manifold section 31 is sealed by a
sealing film 41. The fixed plate 42 is formed of a rigid material
such as metal. A region opposing the manifold 100 of the fixing
plate 42 becomes an opening section 43 which is completely removed
in the thickness direction. Therefore, one surface of the manifold
100 is sealed with only the sealing film 41 having the
flexibility.
[0054] In addition, although not shown in the drawings, a drive
circuit for driving a plurality of the piezoelectric elements 300
is fixed onto the protection substrate 30, and the drive circuit
and a lead electrode 95 are electrically connected to each other
via the connection wire made of a conductive wire such as a bonding
wire.
[0055] In the ink jet type recording head I of the present
embodiment like that, an ink is taken in from an ink inlet
connected to an external ink supply unit (not shown), and after the
inside from the manifold 100 to the nozzle 21 is filled with the
ink, in accordance with a recording signal from the drive circuit
120, a voltage is applied to between the first electrode 60 and the
second electrode 80, each of which corresponds to the pressure
generation chamber 12. Thereby the vibration plate 50 together with
the piezoelectric element 300 flexibly deforms to increase the
pressure in the pressure generation chamber 12 and thus, ink
droplets are ejected from the nozzle 21.
[0056] Here, a method of manufacturing the piezoelectric element of
the ink jet type recording head I of the present embodiment will be
described with reference to FIGS. 5A to 7B.
[0057] First, as shown in FIG. 5A, a silicon dioxide film 151 made
of silicon dioxide (SiO.sub.2), which configures the elastic film
51 on the surface of a wafer 110 for the flow path forming
substrate which is a silicon wafer in which a plurality of the flow
path forming substrates 10 are integrally formed is formed.
[0058] Then, as shown in FIG. 5B, on the elastic film 51 (silicon
dioxide film 151), a zirconium oxide film 152 configuring the
insulator film 52 is formed. Thereby the vibration plate 50 which
is configured of the elastic film 51 and the insulator film 52 is
formed.
[0059] Then, as shown in FIG. 5C, after forming a first electrode
forming layer 160 made of platinum and iridium on the insulator
film 52, the first electrode forming layer 160 is patterned into a
predetermined shape to form the first electrode 60. That is, the
first electrode 60 is formed by being patterned in a strip shape,
such that the first electrode layer 160 corresponds to each
pressure generation chamber 12. The method of forming the first
electrode forming layer 160 is not particularly limited, but
includes, for example, a sputtering method, a chemical vapor
deposition method (CVD method), and the like. In the present
embodiment, although platinum and iridium are used as the material
of the first electrode 60, the material of the first electrode 60
is not limited thereto and may be only the platinum or iridium, or
may be oxide electrode materials such as oxides of other metal
materials, lanthanum, nickel, and the like.
[0060] Next, as shown in FIG. 5D, for example, a piezoelectric body
layer 170 made of zirconate titanate lead (PZT) or the like, and
for example, a second electrode forming layer 180 made of iridium,
platinum or the like are formed on the entire surface of the wafer
110 for the flow path forming substrate.
[0061] Further, in the method of forming the piezoelectric body
layer 170, in this embodiment, a gel is formed by applying and
drying a so-called sol where a metal organic substance is dissolved
and dispersed in a solvent and further, the gel is baked at a high
temperature, so as to obtain the piezoelectric body layer 170 made
of a metal oxide. In this manner, the piezoelectric body layer 70
is formed using a so-called sol-gel method. Accordingly, the method
of forming the piezoelectric body layer 170 is not particularly
limited, for example, a MOD (Metal-Organic Decomposition) method, a
sputtering method, a PVD (Physical Vapor Deposition) method such as
a laser ablation method, or the like may be used. Further,
materials of the second electrode forming layer 180 and a method of
forming the same are alike when forming the first electrode forming
layer 160.
[0062] Next, as shown in FIGS. 6A and 7A, the second electrode
forming layer 180 and the piezoelectric body layer 170 are
patterned to form a through groove 71 and a through hole 72. In
this manner, the second electrode forming layer 180 and the
piezoelectric body layer 170 are patterned in a lump sum and
thereby the upper surface of the piezoelectric body layer 170 (a
region which particularly becomes an active portion) can be
protected by the second electrode forming layer 180. That is, the
upper surface of the piezoelectric body layer 170 can be protected
from process damage in the patterning process. Further, it is
possible to secure alignment accuracy between the piezoelectric
body layer 70 and the second electrode 80. In addition, a method of
etching the second electrode forming layer 180 and the
piezoelectric body layer 170 includes for example, a dry etching
such as reactive ion etching and ion milling.
[0063] Next, as shown in FIGS. 6B and 7B, the second electrode
forming layer 180 is patterned to be separated between the
piezoelectric elements 300 and the second electrode 80 which is an
individual electrode in which each piezoelectric element 300 is
formed. In this case, in this embodiment, an independent electrode
85 is formed at the periphery of the through hole 72. In the
independent electrode 85, the inside and the vicinity of the
through hole 72 are covered with a resist (not shown) during the
patterning of the second electrode 80. That is, the independent
electrode 85 is formed by being excluded from the patterning
target.
[0064] Thus, when patterning the second electrode 80, the first
electrode 60 exposed in the through hole 72 is not etched. For this
reason, it is possible to avoid a disconnection of the first
electrode 60 due to over-etching. Further, it is possible to
further effectively suppress the occurrence of a leakage current
between the first electrode 60 and the second electrode 80. If the
first electrode 60 is over-etched, there is a possibility that the
material of the etched first electrode 60 may adhere (redeposition)
to the surface of the piezoelectric body layer 70 and the like.
Like this, if the material of the first electrode 60 adheres
thereto, the leak current easily occurs between the first electrode
60 and the second electrode 80.
[0065] Further, in order to prevent the over-etching of the first
electrode 60, a region that needs to be protected using the resist
is a region of the through hole 72. However, in consideration of
the alignment accuracy when processing, in practice, a vicinity
region that includes the through hole 72 needs to be protected
using the resist. As the result, after patterning the second
electrode forming layer 180, the material configuring the second
electrode 80 remains in the vicinity of the through hole 72 and
thus the independent electrodes 85 surrounding the through hole 72
are formed.
[0066] Further, in the present embodiment, the second electrode 80
has a wide width portion 81 outside the pressure generation chamber
12. When patterning the second electrode forming layer 180 to form
the second electrode 80, in order to reliably separate the second
electrode forming layer 180 at a desired position, in consideration
of positional accuracy of the resist, a region opposing the second
electrode forming layer 180 and its outside region, for example, a
region opposing the through groove 71 (the dashed line region in
FIG. 7B) need to be etched at the same time. If only the second
electrode 80 is etched, there is a possibility that the material of
the second electrode 80 may remain in the vicinity of the
longitudinal end of the through groove 71 and thus a short circuit
may occur between the adjacent piezoelectric elements 300.
[0067] Further, when etching the predetermined region, the
insulator film 52 exposed in the through groove 71 is also etched
therewith. At this time, if the insulator film 52 opposing the
pressure generation chamber 12 is etched, the vibration plate
becomes thinner. Accordingly, there is a possibility that a
deformation stress may be concentrated and thus cracks may occur
when driving the piezoelectric elements 300. For this reason, it is
preferable that the predetermined region be not overlapped with the
pressure generation chamber 12. In addition, considering the resist
alignment accuracy (accurate alignment of the through groove 71 in
the width direction) with respect to the through groove 71, it is
preferable that the predetermined region have a narrower width than
that of the through groove 71. Similarly, if the width of the
predetermined region is caused to be narrower than the width of the
through groove 71, the wide width portion 81 is formed on the
second electrode 80.
[0068] Thereafter that, as shown in FIG. 6C, after forming a wire
metal layer 190 made of gold (Au) over the entire surface of the
wafer 110 for the flow path forming substrate, a connection wire 90
and each lead electrode 95 is formed by patterning the wire metal
layer 190 into a predetermined shape.
[0069] As described above, in the invention, the independent
electrode 85 independent from the second electrode 80 which is
provided on the piezoelectric body layer 70. For example, in the
present embodiment, the independent electrode 85 is provided at the
periphery of the through hole 72 configuring the exposure portion
61 to which the surface of the first electrode 60 is exposed. As a
result, it is possible to suppress the occurrence of the leakage
current between the first electrode 60 and the second electrode 80
which drive the piezoelectric element 300. Therefore, the
destruction of the piezoelectric body layer 70 resulting from the
leakage current can be effectively suppressed. In addition, the
disconnection due to over-etching of the first electrode 60, which
occurs during the patterning of the second electrode 80, can be
effectively suppressed.
[0070] As described above, an embodiment of the invention has been
described, but the invention is not limited to the above described
embodiment of the invention.
[0071] For example, as shown in FIGS. 8A and 8B, the first
electrode 60 may be formed in a comb-teeth shape so as to be
continuous outside the pressure generation chamber 12 and a second
connection wire 91 may be further provided on the piezoelectric
body layer 70 between each of the lead electrodes 95 so that the
second connection wire 91 is connected to the first electrode 60
via a second through hole 73 formed on the piezoelectric body layer
70. Thereby it is possible to further decrease a resistance value
of the common electrode of the piezoelectric elements 300. Then, in
a case of such a configuration, an independent electrode 85A which
is independent from the second electrode 80 is also provided at the
periphery of the second through hole 73, and thereby the leakage
current occurring between the first electrode 60 and the second
electrode 80 can be effectively suppressed.
[0072] Further, in the embodiment described above, an example of
the configuration where a connection wire 90 is connected to the
first electrode 60 through the through hole 72 provided in the
piezoelectric body layer 70 has been illustrated, but the
connection structure between the first electrode 60 and the
connection wire 90 is not limited thereto. For example, as shown in
FIGS. 9A and 9B, the end of the first electrode 60 may be further
extended to the outside than the end of the piezoelectric body
layer 70 so as to form the exposure portion 61 and thus using the
exposure portion 61, the first electrode 60 may be connected to the
connection wire 90. Even in this case, since the independent
electrode 85A is provided on the end of the piezoelectric body
layer 70 which forms the exposure portion 61, the destruction of
the piezoelectric body layer 70 resulting from the leakage current
can be suppressed similarly to the embodiment described above.
[0073] Further, for example, as shown in FIG. 10, the ink jet type
recording head I having such a configuration is mounted on the ink
jet type recording apparatus II. A recording head unit 1 having the
ink jet type recording head I is provided to have a detachable
cartridge 2 configuring an ink supply unit, and a carriage 3 on
which the recording head unit 1 is mounted is provided so as to be
movable in the axial direction toward a carriage shaft 5 attached
to an apparatus main body 4. The recording head unit 1 ejects a
black ink composition and a color ink composition, for example.
[0074] Then, a drive force of a drive motor 6 is transmitted
through a plurality of gears (not shown in drawing) and a timing
belt 7 to the carriage 3, and thereby the carriage 3 on which the
recording head unit 1 is mounted is moved along the carriage shaft
5. On the other hand, a platen 8 is provided at the apparatus main
body 4 along the carriage shaft 5 so that a recording sheet S which
is a recording medium such as paper that is fed by a paper feed
roller (not shown in drawing) is transported by being wounded
around the platen 8.
[0075] Then, in the invention, as described above, since the
destruction of the piezoelectric element 300 configuring the ink
jet type recording head I can be suppressed, it is possible to
realize an ink jet type recording apparatus II with an improved
durability and reliability.
[0076] In addition, in the ink jet type recording apparatus II
described above, an example of the ink jet type recording head I
(recording head units 1A and 1B) is mounted on the carriage 3 to
move in the main scanning direction have been illustrated, but it
is not particularly limited thereto. For example, while the ink jet
type recording head I is being fixed, printing may be performed by
merely moving the recording sheet S such as paper in the
sub-scanning direction. Therefore, it is possible to apply the
invention even to a so-called line type recording apparatus.
[0077] In addition, in the above embodiment, the ink jet type
recording head has been described as an example of a liquid
ejecting head, but the invention is widely intended for the entire
liquid ejecting heads and liquid ejecting apparatuses having the
same head and thus it is of course possible to apply even to a
liquid ejecting head that ejects a liquid other than the ink. The
examples of the other liquid ejecting head include various
recording heads used in an image recording apparatus such as a
printer, a color material ejecting head used in manufacturing a
color filter such as a liquid crystal display, an electrode
material ejecting head used in forming electrodes such as an
organic EL display, and a FED (field emission display), and a
bio-organic substance ejecting head used in manufacturing a
bio-chip, and the like.
[0078] In addition, the invention is not limited to the
piezoelectric element used in the liquid ejecting head, but may
also be used for other devices. As the other devices, for example,
an ultrasonic device of an ultrasonic transmitter, an ultrasonic
motor, and a piezoelectric transformer and the like may be
included. In addition, the invention may be applied to the
piezoelectric element used as a sensor. As a sensor where the
piezoelectric element is used, for example, an infrared sensor, an
ultrasonic sensor, a thermal sensor, a pressure sensor, a
pyroelectric sensor and the like may be included.
[0079] The entire disclosure of Japanese Patent Application No.
2012-024885, filed Feb. 8, 2012 is incorporated by reference
herein.
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